Map data used in the related art in a navigation system installed in a vehicle are compiled in information units (layers) each defined in correspondence to a specific map scaling factor, with each layer of data containing information divided in units (meshes) matching a predetermined area range. Road data indicating road shapes, road types and the like, background data indicating the shapes and types of background objects other than roads and name data indicating the names of the roads and the background objects in the road data and the background data are provided in correspondence to each match.